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  • 1
    Electronic Resource
    Electronic Resource
    Resonant phase shift technique for the measurement of small changes in grounded capacitors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1267-1272 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple technique has been developed for the high resolution measurement of small changes in capacitors which have one grounded electrode. The capacitor is arranged to be the tuning element in a series resonant LC tank circuit that is driven by a transistor emitter follower. Signal information is provided by observing the phase shift in the transistor collector current that results from any small change in the capacitor value. Implementation is simple, readily analyzable, provides good diagnostics, is easily multiplexed into arrays, and has potential applications in a number of areas including high resolution proximity sensing, capacitive topography, atomic force microscopy, and capacitor microphones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141224
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  • 2
    Electronic Resource
    Electronic Resource
    A simple, inexpensive, hyperthermal atomic oxygen sensor (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3557-3562 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: With the increasing duration of space flights, the development of a permanent facility in space, and the increasing use of ground-based hyperthermal atomic oxygen sources there is a need for a simple instrument to provide long-term monitoring of the beam flux. Such an instrument can also be used as a diagnostic tool to investigate the material degradation process. Reliance on models of the upper atmosphere to determine the fluence of atomic oxygen is not only necessarily complex but also imprecise due to the strong dependence of oxygen concentration on day/night, latitude, and solar activity. Mass spectroscopy, the traditional method for determining the gas phase species densities at low pressure, is not only expensive but is limited in the area that it can monitor as well as subject to effects of material degradation. Our group has developed a simple and inexpensive dosimeter to measure the atomic oxygen fluence via the change in resistance as the sensor element is gradually oxidized. The sensors consist of thin-film circuit elements of selected material deposited on a suitable substrate. Four-point resistance measurements are used to monitor the change in sensor resistance with respect to time. Results obtained from silver and carbon dosimeters flown on STS-46 (CONCAP-II-01) indicate that such sensors are sensitive enough to monitor the diurnal variations in atomic oxygen distribution and sufficiently durable to last the lifetime of a mission. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148322
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of edge turbulence in tokamaks, stellarators, and reversed-field pinches* (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2491-2497 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Edge equilibrium, turbulence and transport related plasma parameters from the Advanced Toroidal Facility (ATF) [Fusion Technol. 10, 179 (1986)] torsatron, the ZT-40M [Fusion Technol. 8, 1571 (1985)] reversed-field pinch, the Phaedrus-T [Nucl. Fusion 32, 2040 (1992)] tokamak, the Texas Experimental Tokamak (TEXT) [Nucl. Technol. Fusion 1, 479 (1981)], and the Tokamak Fusion Test Reactor (TFTR) [in Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, p. 9] have been obtained using a standardized Langmuir probe array and a consistent set of data analysis packages. Additional data from some other devices have also been furnished via private communications and incorporated from published results. Experimental results over a wide range of parameters are compared and the turbulence contribution to edge transport are assessed. Certain physical properties that are relevant to the modeling of edge turbulence are identified: namely, shear decorrelation of turbulence, the role of resistive dissipation and electron parallel thermal conduction, radial mode structure in sheared magnetic field, and electromagnetic contribution to the parallel Ohm's law.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860734
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  • 4
    Electronic Resource
    Electronic Resource
    A rocking beam electrostatic balance for the measurement of small forces (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 705-709 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: There exists interest in the measurement of small forces for applications such as microtopography of semiconductor devices and atomic force microscopy. A new method is introduced here in which a small silicon beam, that is acted on by the external force of interest, has its position sensed by an rf phase shift technique. The position information in turn is fed back via electrostatic forces to continuously rebalance the beam about its central support. This force-feedback approach provides high sensitivity, submillisecond response, inherent force calibration, and electronically controlled stiffness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142071
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  • 5
    Electronic Resource
    Electronic Resource
    Phase dynamics of Kármán vortices in cylinder wakes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 91-96 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temporal evolution of Kármán vortex shedding patterns in the wake of a cylinder placed at right angles to a uniform flow is studied for Reynolds numbers (based on cylinder diameter) between 80 and 140. Focusing on the dynamics of the vortex shedding phase in the wake planview (the plane spanned by the free-stream direction and the cylinder axis) we study experimentally and model the response of shedding patterns to time-dependent boundary conditions imposed at the cylinder ends. By appropriate impulsive changes of end conditions, spanwise wave number "shocks'' can be produced that travel along the cylinder span. These shock experiments, together with data from steady oblique shedding patterns, are used to determine the parameters for the spanwise Ginzburg–Landau model, which has already been used successfully to describe many of the phenomena observed in cylinder wakes. We then demonstrate experimentally that, in analogy to gasdynamics, it is also possible to produce "expansion waves'' of the spanwise wave number, which are well described by the Ginzburg–Landau model without further adjustment of its parameters. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868817
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  • 6
    Electronic Resource
    Electronic Resource
    Quality Changes in Diced Onions Stored in Film Packages (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 59 (1994), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of a potassium permangenate gas absorbent and storage at 2°C on quality changes in modified atmosphere packaged diced onions was studied. A 3 mil packaging film resulted in equiIibrated O2 of 2.65% and CO2 level of 3.65%. Gas absorbent resulted in reduced ethylene, carbon dioxide and sulfur volatiles. Maximum shear force values and total phenolics increased during storage, but were not affected by gas absorbent. Glucose and fructose concentrations declined within one day after processing, which coincided with an increase in sucrose. Sugar concentrations remained stable thereafter, and were not affected by gas absorbent. Microbe colony forming units (CFU) increased during storage to 5.8 in controls and 7.1 (log CFU/g) in absorbent treated samples after 10 days at 2°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1994.tb06909.x
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